Because the easy thing to do would be to simply laugh along with his story and miss the larger problems he is skating around. That'd just reinforce the bad attitude. He needs somebody to say look, crappy jobs are part of life, if you want to have a better career instead of keeping a list of gripes learn some interpersonal and professional skills and don't do this again. It's not something to praise. You deserve better.
I guess why I'm harsher than usual on this article is that consulting is basically being somebody's smart friend for money. They pay you, and you're supposed to put their interests above your own for a period of time (within reason, of course). Friends don't keep running lists of grievances against each other -- it's counterproductive and it makes interpersonal progress damn near impossible.
I have a good friend who I went to school with. He is a card-carrying conservative evangelical holy-roller. Even became a minister. He also does network and server administration. His current gig? Working as network admin inside the beltway for one of the most liberal, anti-religious organizations on the planet (You'd instantly recognize the name)
Does he keep a list of how offensive these people are to him? Not at all. His job is to put their interests first and to take care of them as a friend. They like him so much he's been there over ten years and moved up a couple of spots.
You learn to deal with adverse conditions without holding grudges, keeping logs, or keeping it all inside. That's not an easy lesson to learn, but it's critical. I was trying to cut the guy some slack by pointing out that facing your problems and growing from them is the better way long-term. You don't want to get into a pattern where you're the smart genius and all the gigs you've worked were full of barely functional morons. That's Dilbert, not real life.
Sorry about running on so long. It just got under my skin as a professional skills thing. Everybody has war stories, but you tell them knowing that from the other side, you were the moron. I didn't see that.
EDIT: "Giving somebody a break"= doing the harder thing for you to do which results in the easier path for the person involved.
You just made my brain reboot. How does that make any sense?